Re: [PATCH 1/3] dt-bindings: phy: qcom,qmp-pcie: add optional current load properties

Manivannan Sadhasivam
2024-12-11T08:24:20Z

On Wed, Dec 11, 2024 at 09:09:18AM +0100, Krzysztof Kozlowski wrote:
> On 11/12/2024 07:20, Manivannan Sadhasivam wrote:
> > On Thu, Dec 05, 2024 at 11:23:11AM +0100, Krzysztof Kozlowski wrote:
> >> On Wed, Dec 04, 2024 at 06:52:47PM +0800, Ziyue Zhang wrote:
> >>> On some platforms, the power supply for PCIe PHY is not able to provide
> >>> enough current when it works in LPM mode. Hence, PCIe PHY driver needs to
> >>> set current load to vote the regulator to HPM mode.
> >>>
> >>> Document the current load as properties for each power supply PCIe PHY
> >>> required, namely vdda-phy-max-microamp, vdda-pll-max-microamp and
> >>> vdda-qref-max-microamp, respectively.PCIe PHY driver should parse them to
> >>> set appropriate current load during PHY power on.
> >>>
> >>> This three properties are optional and not mandatory for those platforms
> >>> that PCIe PHY can still work with power supply.
> >>
> >>
> >> Uh uh, so the downstream comes finally!
> >>
> >> No sorry guys, use existing regulator bindings for this.
> >>
> >
> > Maybe they got inspired by upstream UFS bindings?
> > Documentation/devicetree/bindings/ufs/ufs-common.yaml:
> >
> > vcc-max-microamp
> > vccq-max-microamp
> > vccq2-max-microamp
>
> And it is already an ABI, so we cannot do anything about it.
>
> >
> > Regulator binding only describes the min/max load for the regulators and not
>
> No, it exactly describes min/max consumers can use. Let's quote:
> "largest current consumers may set"
> It is all about consumers.
>
> > consumers. What if the consumers need to set variable load per platform? Should
>
> Then each platform uses regulator API or regulator bindings to set it? I
> don't see the problem here.
>
> > they hardcode the load in driver? (even so, the load should not vary for each
> > board).
>
> The load must vary per board, because regulators vary per board. Of
> course in practice most designs could be the same, but regulators and
> their limits are always properties of the board, not the SoC.
>

How the consumer drivers are supposed to know the optimum load?

I don't see how the consumer drivers can set the load without hardcoding the
values. And I could see from UFS properties that each board has different
values.

- Mani

--
மணிவண்ணன் சதாசிவம்